1. Field of the Invention
The invention relates to biodegradable copolymers of vinyl esters with cyclic ketene acetals.
2. Related Art
It is known that polymers whose carbon backbone is interrupted by functional groups such as ester, amide, carbonate, urethane or ether groups and whose hydrocarbon moieties between the functional groups are predominantly of an aliphatic nature can be degraded by microorganisms (S. J. Huang, Encyclopedia of Polymer Sciences Vol. 2, 220-243). In contrast, polyolefins having a purely carbon backbone are resistant to microbial attack. An exception is, for example, polyvinyl alcohol, which is completely degraded to carbon dioxide and water after oxidative cleavage (T. Suzuki et al., J. Appl. Poly. Sci., Poly. Symp. 35 (1973), 431). In contrast, polyvinyl acetate is only degraded with difficulty, since it first has to largely hydrolyze to polyvinyl alcohol.
W. J. Bailey et al., J. Polym. Sci. Chem. Ed. 20 (1982), 3021, describes the preparation of vinyl acetate copolymers containing 33 and 49 mol % of 2-methylene-1,3-dioxepane. The biodegradability of these copolymers is assumed but not tested. The disadvantages of this method are the low degrees of conversion (52 and 68%) at extremely long polymerization times (up to 48 hours) and the low molecular weights caused by the high proportion of initiator (1.0 and 1.2 mol %).
JP-A 02/214719 (Derwent Abstract) discloses polymers of olefins, acrylates, vinyl esters or styrenes with 2-methylene-1,3-dioxepane as hydrolyzable polymers for use in marine paints.